In optical systems, it is sometimes necessary to accurately position a focused beam of radiation with respect to a relatively small target, such as the core of an optical fiber. The traditional approach has been to effect relative movement between the target and the optical system that generates the focused beam. This typically requires a mechanism that can effect the relative movement with a level of precision and accuracy that is greater than the required adjustment between the beam and target. These movement mechanisms can be relatively expensive, and can also exhibit instability. Consequently, although pre-existing techniques for positioning a focused beam in relation to a target have been generally adequate for their intended purposes, they have not been satisfactory in all respects.